The present invention relates to an improved adjustable fulcrum hammer.
Conventional hammers are made with a handle extending between a grip at one end and a head having a claw and striking surface affixed to the other end. The claw is typically used for prying, particularly removing nails and the like. The upper surface of the head between the claw and striking surface normally serves as the fulcrum.
One of the drawbacks of such conventional hammers is that the distance between the upper surface of the head which serves as the fulcrum and the point at which the claw grasps a nail or the like to be pried often is not sufficient to completely remove the nail. When prying other objects bending and damage to the object being pried may result if the distance is not sufficient. On the other hand, providing a claw which extends a considerable distance from the handle makes the tool awkward to use and even dangerous.
To overcome this problem, adjustable fulcrum hammers have been developed. These hammers all include some kind of member which slides into and out of the handle between the striking surface and the claw to provide a fulcrum which can be adjusted along the direction of the handle as necessary. Although a number of different configurations have been suggested, none have proven completely satisfactory in use or suffered other drawbacks which have precluded their commercial acceptability.
For example, the patent to Eveleth U.S. Pat. No. 540,967 describes a hammer of this type in which a plunger is provided with a plurality of notches which can be selectively engaged by means of a finger operated latch having a portion extending through the handle between its ends. A cushion is provided on the far end of the plunger for minimizing damage to the surface which is contacted and which thus serves as the fulcrum. A spring attaches to the other end of the plunger urging it outward.
This type of adjustable fulcrum hammer has a considerable number of disadvantages. First, the plunger is difficult to manufacture and cannot be obtained as a standard part. The notches weaken the plunger and provide places where it can easily break as well as interrupt spacing. The plunger must be kept in an orientation where the latch will mesh with one of the notches, thus complicating the internal construction of the handle. The notches will wear and eventually the plunger will not be able to lock firmly in position. Finally, while using this configuration of parts, if the latch is accidentally struck during rebounding off the strike surface the fulcrum will prematurely eject. Other adjustable hammers of interest are described in the patents to Martin U.S. Pat. No. 619,325, Palmer U.S. Pat. No. 856,097, Williams U.S. Pat. No. 2,741,456, Thayer U.S. Pat. No. 35,715, Frey U.S. Pat. No. 107,729, Carlson U.S. Pat. No. 1,737,958, Balkus, Jr. U.S. Pat. No. 3,885,772, and Thomson U.S. Pat. No. 1,226,413.
The present invention relates to an improved fulcrum handle of the type generally described above. However, in the present invention, a fulcrum rod which is preferably in one embodiment a solid cylindrical rod is mounted to be fully rotatable within the interior space in the handle and extending through a bore in the hammer head to the upper surface thereof. A set screw in this embodiment preferably provided with a lock washer is used to lock the rod in any desired position. The set screw provides a lock washer positioned between the hammer handle and the set screw head so as to provide a locking arrangement of the fulcrum member and set screw so as not to vibrate loose and prematurely eject. Since the rod can be rotated within the bore, and since the set screw can contact any position difficulties of wear, weak points are avoided. No complex construction for the fulcrum member or the interior of the handle is required. The present invention can be easily and economically constructed from simple, readily available parts.
According to one embodiment of the present invention, a claw hammer head is fixed about a handle having a grip at one end with the head fixed about the other end. The fulcrum rod extends through a bore into the interior space within the handle which handle is preferably formed as a hollow cylinder. A set screw extends through the handle between the ends thereof, preferably in a built up region having thicker walls for contacting and locking the rod in any desired position. The fulcrum member at the end of the rod remote from the handle is formed of elastomeric material such as rubber or the like so as to avoid marring the surface which it contacts. The fulcrum member at the end of the rod housed within the handle is provided with a bore which allows the urging spring to engage with the fulcrum member end so that the fulcrum member will not completely eject out of the head of the hammer.
According to another embodiment of the present invention, a fulcrum rod is provided with a tap-like configuration and includes opposing planar portions and opposing threaded portions extending down the fulcrum member's length or at least a predetermined portion thereof. A die region within the interior of the hammerhead is provided with the same opposing planar portions and opposing threaded portions configuration as provided with the fulcrum rod so as to engagingly cooperate therewith. The cooperation between the opposing planar and threaded portions of the fulcrum member and die acts as the locking and adjusting means of the fulcrum member in a manner that will become more clear from the description thereof below. A spacing washer or sleeve is provided in the interior space in the handle and contacts that portion of the fulcrum member housed therein. This interior spacing washer prevents the interior portion of the fulcrum member from wobbling as well as preventing free rotation of the fulcrum member in its locked position during normal use of the hammer.